2.1 Study sites
Plateau pikas can live in various habitats with different soil types, topographies, and microclimates. To identify a general pattern of how plateau pika disturbance influences the ecosystem services of alpine grasslands, this study selected five sites with different alpine grassland types, topographies and microclimates as field survey areas. These five survey sites have a similar typical plateau continental climate, with mean annual temperatures of 3.3℃ in Luqu (102°10´-102°52´E, 34°16´-34°37´N), 2.0℃ in Gangcha (99°53´-100°36´E, 37°17´-37°29´N), 2.0℃ in Haiyan (100°37´-100°58´E, 36°51´-37°14´N), 2.1℃ in Qilian (99°28´-100°54´E, 37°58´-38°27´N), and 3.7℃ in Gonghe (99°41´-100°12´E, 36°21´-36°36´N). These survey areas range in elevation from 3000 m at the Gangcha survey site to 3550 m at the Luqu survey site, with average annual precipitation varying from 350 mm at the Gonghe survey site to 630 mm at the Luqu survey site. According to the Chinese soil classification system (Gong, 2001), the soil type is alpine meadow soil in the five survey sites, similar to Cambisol in the WRB soil classification system. Soil nutrients are different among the five survey site areas (Pang et al., 2020a, 2020b).
The five field survey areas were placed in cold-season areas, which were fenced from mid-April to September, and fences were opened to grazing yaks with a 3.4 yaks ha-1 grazing stock rate from mid-October to early April (Zhang et al., 2020). The alpine grasslands in the five survey areas were dominated by Kobresia humilis andKobresia pygmaea . Plateau pikas were the only small burrowing herbivores in the field survey areas, and their population generally peaked in August (Pang et al., 2020a, 2020b; Qu et al., 2013), implying that sampling plants and soil in August may best reflect the effect of plateau pika disturbance on alpine grassland ecosystem services.